Research On The Facility And Preparation Of CBN Film By DC Jet Plasma CVD

Cubic boron nitride (cBN) has excellent physical and chemical properties, such as ultrahighhardness, good abrasion resistance, outstanding antioxidant ability, uneasy reaction with ferrousmaterials as well as p and n doping. It has broad prospects in the application of mechanical machining,optical and electronic fields. In order to investigate the preparation process of cBN, research wascarried out in this paper. The main work and results obtained are as follows:1. The principle of DC jet plasma CVD deposition equipment was studied, and its upgradingprocess based on the requirements of cBN preparation was carried out, including the addition of H2, N2and BF3gas lines, substrate bias device and tail gas treatment system. And the influences of Ar/N2ratio, bias voltage, and BF3flow on the plasma arc stability were studied. The adapted parameters forstable plasma-arc were as follows: volume pressure4kPa, pump pressure9kPa, Ar flow3~4.5slm, N2flow1~2slm, BF310~20sccm (10%in Ar), substrate bias lower than-75V.2. Finite elements model of deposition chamber was established, and the simulation was carriedout by Fluent. In the simulation, influences of different distances between anode and substrate holder,different Ar/N2ratios and different holder on temperature field and flow field were studied. The resultsshow that the temperature and pressure of substrate surface would be drastically decreased by thereduction of distance between anode and substrate holder, and slowly decreased by the increase ofAr/N2ration. And comparing with Mo holder, Cu holder resulted in a sharp decrease of temperature.3. The preparation of cBN was carried out on Si, Si/diamond, carbide/diamond, and Mo/diamond.The influences of bias voltage and substrate temperature upon the deposition of cBN on Si substratewere investigated, the adequate parameters in the present system were as follows: temperature860°Cand substrate bias-60V. Deposition of cBN on Si/diamond was done, film was reunion-like. Thecarbide was overall heated in the plasma, which made the surface temperature too high, resulting in thestrong etching of the diamond layer on the surface, and that hindered the nucleation and growthprocess of cBN. The diamond layer on Mo was also etched in the plasma and nano cBN grains wasfound.